Summary: Our long-term goals are to identify the genetic basis for disease traits in the lysosomal storage disorder Niemann-Pick Type C1 (NPC1), to study NPC1 disease pathogenesis, and to develop diagnostic and treatment paradigms for this disease. NPC1 is an autosomal recessive, neurovisceral lipid storage disorder that presents with variable hepatosplenomegaly, vertical supranuclear ophthalmoplegia, progressive ataxia, dystonia, and dementia. Our group has a long-term commitment to studying several aspects of this disease including those involving genetic diagnostic, prognostic and therapeutic approaches. The approaches we develop for assessing and treating NPC1 disease will also be used as a model for other rare human diseases. We have also published a study where we generated an induced pluripotent stem cell line from a subject homozygous for the most frequent NPC1 mutation (p.I1061T) and subsequently created a stable line of neural stem cells (NSCs). These NSCs were then used to create neurons as an appropriate disease model. NPC1 neurons display a premature cell death phenotype, and gene expression analysis of these cells suggests dysfunction of important signaling pathways, including calcium and WNT. The clear readout from these cells makes them ideal candidates for high-throughput screening and will be a valuable tool to better understand the development of NPC1 in neural cells, as well as to develop better therapeutic options for NPC1. We have also applied these techniques to the study of two related disorders, Smith-Lemli-Opitz syndrome and glucocerebrosidase deficiency. Treatments currently being tested may have associated complications (cyclodextrin requires continuous delivery and may be associated with hearing loss) or only be effective in subsets of patients (HDACi may only be effective on those with mutations that affect folding/trafficking). We have published a study examining cyclodextrin based therapies. New therapies for patients with NPC need to be developed. While gene therapy for NPC was previously considered as a questionable intervention due to limitations of the field, alternative AAV serotype vectors that can transduce neurons after either systemic or local delivery have mandated a critical reappraisal of gene therapy as a possible treatment for NPC, especially since vectors in this class have proveneffective in treating neurodegenerative disorders. As a critical first step that would help enable the development of a new class of gene therapy for patients, we are assessing adeno-associated virus (AAV) gene therapy as a novel therapy for NPC using a well studied murine model. We are comparing the effectiveness of systemic and intracranial injections of AAV serotypes 9 and rh10 vectors, configured to express the endogenous human NPC1. We have published our first study on this approach and submitted a patent application.